The effect of 313 nanometer light on initiation of replicons in mammalian cell DNA containing bromodeoxyuridine.

After unifilar substitution of thymine with bromouracil in either human HeLa or bovine cells, exposure to 313 nm light inhibits initiation of clusters of replicons. Since this treatment results in damage only to DNA and because the effect is the same as observed after 100-1000 rads of X-ray irradiation to the same cells, we infer that the effect of the later treatment is also mediated almost exclusively by DNA damage.